Convective Parameterization Optionsin WRF V3.4

Jimy DudhiaNCAR/NESL/MMM

with help from Ming Chen

Cumulus schemes in V3.4cu_physics

Scheme Cores Moisture Tendencies

Momentum Tendencies

Shallow Convection

1 Kain-Fritsch Eta ARW NMM Qc Qr Qi Qs no yes2 Betts-Miller-Janjic ARW NMM - no yes3 Grell-Devenyi ARW NMM Qc Qi no no4 Old Simplified

Arakawa-Schubert

ARW NMM Qc Qi yes (NMM) yes (ARW)

5 Grell-3 ARW Qc Qi no yes6 Tiedtke ARW Qc Qi yes yes

7 Zhang-McFarlane ARW Qc Qi yes no14 New SAS ARW Qc Qi yes yes

84 New SAS (HWRF) ARW NMM Qc Qi yes (NMM) yes (ARW)

99 Old Kain-Fritsch ARW Qc Qr Qi Qs no no

Kain-Fritsch (KF)• As in MM5 and Eta/NMM ensemble version• Includes shallow convection• Low-level vertical motion in trigger function

– Also new Ma-Tan trigger option with perturbation based on local average moisture advection (kfeta_trigger=2)

• CAPE removal time scale closure• Mass flux type with updrafts and downdrafts, entrainment

and detrainment• Includes cloud, rain, ice, snow detrainment• Clouds persist over convective time scale (recalculated every

convective step in NMM)• Old KF is also an option in WRF

Betts-Miller-Janjic (BMJ)• As in NMM (NAM) operational model (Janjic 1994)• Adjustment type scheme• Deep and shallow profiles• BM saturated profile modified by cloud efficiency, so

post-convective profile can be unsaturated in BMJ• No explicit updraft or downdraft• No cloud detrainment• Scheme changed significantly since V2.1

Grell-Devenyi Ensemble (GD)• Used in Rapid-Refresh operational model (NOAA/ESRL)• Multiple-closure (CAPE removal, quasi-equilibrium,

moisture convergence, cloud-base ascent) - 16 mass flux closures

• Multi-parameter (maximum cap, precipitation efficiency) - e.g. 3 cap strengths, 3 efficiencies

• Explicit updrafts/downdrafts• Includes cloud and ice detrainment• Mean feedback of ensemble is applied• Weights can be tuned (spatially, temporally) to optimize

scheme (training)

Simplified Arakawa-Schubert (SAS)• Used in operational HWRF hurricane model• Quasi-equilibrium scheme• Related to Grell scheme in MM5• Random cloud top• Includes cloud and ice detrainment• Downdrafts and single, simple cloud• Shallow convection is by enhanced mixing (in ARW only)• Part of HWRF physics in NMM up to V3.3• Momentum transport in NMM only

Grell-3d (G3)• As GD, but slightly different ensemble (for RR model)• Includes cloud and ice detrainment• Subsidence is spread to neighboring columns

– This makes it more suitable for < 10 km grid size than other options

– cugd_avgdx=1 (default), 3(spread subsidence)• ishallow=1 option for shallow convection• Mean feedback of ensemble is applied• Weights can be tuned (spatially, temporally) to

optimize scheme (training)

Tiedtke (TDK)U. Hawaii version• Mass-flux scheme• CAPE-removal time scale closure• Includes cloud and ice detrainment• Includes shallow convection• Includes momentum transport• New in V3.3• V3.4 changes entrainment/detrainment adds trigger

choice (moisture convergence or dilute parcel testing)

Zhang-McFarlane (ZM)CAMZM scheme • Mass-flux scheme • CAPE-removal time-scale closure• From current CESM 1.0 climate model physics• Includes cloud and ice detrainment• Includes momentum transport with pressure term• New in V3.3

New SAS (NSAS)• Quasi-equilibrium scheme• Updated from SAS for current NCEP GFS global

operational model• Includes cloud and ice detrainment• Downdrafts and single, simple cloud (no random top)• New mass-flux type shallow convection (changed

from SAS)• Momentum transport with pressure-gradient term• New in V3.3• In V3.4 there is also an HWRF version of this

Bretherton-Park Shallow CuCAM UW shallow convection (Bretherton and Park, U.

Washington)• To be used with a TKE PBL scheme and a deep

scheme with no shallow convection (e.g. CESM Zhang-McFarlane)

• From current CESM climate model physics• Shallow convection driver added in V3.3• Other options such as Grell ishallow to be moved

here in the future

Cumulus schemes in V3.4cu_physics

Scheme Cores Moisture Tendencies

Momentum Tendencies

Shallow Convection

1 Kain-Fritsch Eta ARW NMM Qc Qr Qi Qs no yes2 Betts-Miller-Janjic ARW NMM - no yes3 Grell-Devenyi ARW Qc Qi no no4 Old Simplified

Arakawa-Schubert

ARW NMM Qc Qi yes (NMM) yes (ARW)

5 Grell-3 ARW Qc Qi no yes6 Tiedtke ARW Qc Qi yes yes

7 Zhang-McFarlane ARW Qc Qi yes no14 New SAS ARW Qc Qi yes yes

84 New SAS (HWRF) ARW NMM Qc Qi yes (NMM) yes (ARW)

99 Old Kain-Fritsch ARW Qc Qr Qi Qs no no

Tests with V3.3 (April 2011)

• A mid-latitude US continental convection case for 11-12 June 2011 at 12 km grid size, 24 h run plus a 3 km explicit-only simulation

• Tropical TWP-ICE mostly oceanic active monsoon case for January 22-25 2006 at 27 km, 72 h run

• Compare heating and precipitation characteristics– Heating profile (convective and total)– Precipitation (convective, non-convective fractions)– Precipitation bin histograms (convective, non-convective)

Obs (ST4) KF BMJ G3

Tiedtke NSAS SAS ZM

12 hour Total Precipitation

Ratio of conv / total precip 3 h precip

Domain-Averaged Precipitation Forecasts

NSAS

Tiedtke

KF

ZM

Ratios of Convective / Total Precip Over Precip Bins

NSAS

ZM

Domain- and Time-Averaged Heating and Moistening Profiles

T, convective T, total Qv

NSAS

ZM

NSAS

G3

BMJ

12 h total precipitation

3 km

explicit

KF KF-trig

with CPSObs (ST4)

observed

Domain-Averaged Heating ProfilesFrom Various CPS and Cloud-Resolving Runs

explicitNSAS

G3

Mid-latitudeat 12 km

Tropical/Sub-tropicalat 27 km

conv/total 3 h precip

1-day

3-daysZM

SAS

G3

NSAS

TiedtkeZM

KF

Mid-lat 12 km

Tropical / sub tropical 27 km

conv total

conv total

Precipitation Intensity Areas

non-conv

non-conv

24 hr precip bins

24 hr precip bins

Ratios of Convective / Total Precip Over Precip Bins

Mid-Latitude Tropical / Sub-tropical

ZM

NSASSAS

ZM

KF

Convective / Total Precip Over Precip Bins

Mid-Latitude Tropical / Sub-tropical

G3

ZM

convective

total

Mid-lat

Tropical / sub tropical

conv total

conv total

Domain-Averaged Heating Profiles

NSAS

ZM

SASG3

SAS

BMJ

BMJ

ZM

BMJ

ZM + shallow

G3+shallow

Summary• Wide distribution of convective versus non-

convective rainfall fractions• Despite this, similar total rainfalls, patterns, and

heating profiles• Some outliers evident seen in both US and TWP• ZM, Tiedtke: low convective fraction and heating rate• ZM: no intense convective precip (all non-convective)• G3, NSAS: high convective fraction and heating top• G3: high precip and heating rate (tropical)[reduced in V3.3.1]• NSAS: high convective heating and drying rate (mid-lat)• SAS, BMJ: high upper total heating rate• BMJ: effect of no detrained cloud seen in heating profile